Aircraft wheel brake



Jan. 7, 1936. I 's 2,027,210 AIRCRAFT WHEEL BRAKE 2 Filed Dec. 2''(, 1933 6 Sheets-Sheet l INV! NTOR Jan. 7, 1936. J, TAR 2,027,210

AIRCRAFT WHEEL BRAKE Filed Dec. 27, 1933 6 Sheets-Sheet 2 INVBNTOR l a WWW w w 6 Jan. 7, 1936. 1 TARRls 2,027,210

AIRCRAFT WHEEL RAKE Filed Dec. 27, 1933 6 Sheets-Sheet 3 a w A mvcnrron' I w) 1" W mm mvm F. J. TARRIS AIRCRAFT WHEEL BRAKE Jan. 7, 1 936.

6 Sheets-Sheet 4 Filed Dec. 27, 1933 mvzn'ron i H I Jan. 7, 1936. F. J. TARRIS AIRCRAFT WHEEL BRAKE Filed Dec. 2'7, 1933 6 Sheets-Sheet 5 Jan; 7, 1936. F. J. TARRIS 2,027,210

AIRCRAFT WHEEL BRAKE Fi1ed-Dec. 27, 1933 6 sheets-sheet Patented Jan. 7, 1936 PATENT OFFICE Aracam WHEEL BRAKE Frederick'lohn Tari'is, SilvertowmLondon, England, assignor to The India Rubber, Gutta Percha and Telegraph Works Company Limited, Aldwych, London, England, a British .Oom-

Ir ny Application December 27, 1933, Serial No. 104,077

In Great Britain February 15, 1933 j 8 Claims. (Cl. 244 2) This invention forms a continuation in part of the invention forming the subject of U. S. Patent application Serial No.- 654,805 filed February 2,

, 1933, now Patent No. 2,017,928,. and relates to 5 brakes for aircraft wheels and has for its object to provide an improved means whereby when it is desired to turn the aircraft whilst moving along the ground to one side or the other, the brake pressure on the wheels or wheel sets of the undercarriage which are respectively situated on either side of the central vertically and longitudinally extending plane of symmetry can be differentially adjusted.

The invention comprises improvements in or relating to a control mechanism for the operation of aircraft wheel brakes, which control mechanism is of the type comprising a main control device which is operable by the aircraft pilot to control the simultaneous operation of the two brake wheels located on opposite sides of the central longitudinal plane of symmetry of the aircraft;

and a pair of auxiliary control devices one of which communicates with the brake or brakes of the wheel or wheels on the other side of the said plane (referred to hereinafter as one-set of brakes or one brake set), and the other of which communicates with the brake or brakes of the wheel or wheels on the other. side of the said 30 plane, the said auxiliary control devices being mounted in the aircraft so that each may be individually operated for the purpose of producing a differential operation of the two brake sets. This type of mechanism is to be understood as being referred to by the phrase"A control mechanism of the type specified when this phrase is employed in the following specification and appended claims.

In a control mechanism of the type specified the auxiliary control devices are intended to be operated for the purpose of steering when landing, by movement of the rudder-bar or equivalent mechanism of the aircraft and will be so arranged that when the rudder-bar is turned or its equivalent mechanism operatedto steer in one direction that auxiliary control device of the pair provided will be operated which communicates with the corresponding set of brakes, modification of the action of which by the saiddevice aids the said turning movement. Movement of the'rudder-bar or equivalent mechanism to steer in the opposite direction will be arranged to operate the other, control device and produce an opposite differential braking effect.

5 In order that the following specification and appended claims may be brief and clear the term rudder-bar is employed hereinafter to refer to the rudder-bar of the aircraft or to any equivalent device or mechanism and is to be understood as including such equivalent mechanisms.

According to the invention there is provided for the operation of aircraft wheel brakes, a control mechanism of the type specified wherein each auxiliary control device is provided with an actuator which is movable into and out from positions for co-operation with the rudder-bar; said actuators being-such that in the non-co-operative position they will leave the rudder-bar free from encumbrance by them.

According to the invention also, there is provided for the operation of aircraft wheel brakes, a control mechanism of the type specified having means which operatively connect or are capable of operatively connecting the rudder-bar with the auxiliary control devices, wherein each'auxiliary control device serves only brakes on one side of the said plane and comprises means for releasing the braking pressure and an actuator for connecting the said releasing means with the rudderbar whereby movement of the latter can produce a differential braking effect by release of braking pressure in the brakes on one side of the aforesaid plane substantially without alteration of the braking pressure in the brakes on the opposite side.

According to one preferred constructional form of the invention such control mechanisms have each an auxiliary control device comprising a valve controlling the braking pressure in its'respective brake-set and loading means for. the valve operated in accordance with the extent of operation of the main control device. The valve loading means of such a construction may conveniently be connected to the corresponding'actuator so that the said loading means are operated in accordance with the movements of the actuator produced by movement of and by virtue of its co-operation with the rudder-bar.

Preferably the actuators of theauxiliary control devices. in any of the forms of the invention given above are such as to be brought into or out of positions for co-operation with the rudder-bar by operation of the main control device. Preferably also the auxiliary control devices have means to provide an operative condition for the actuators and to release them from thesaid condition, which means are such that the said condition cannot be established for either actuator until the rudder-bar has been moved away from the said actuator to a position at which no differential adconstruction each auxiliary control device conveniently comprises in combination two reciprocable devices one of which is operated by and w the other which controls pressure-fluid passing to the respective brake-set, and a releasable coupling operatively connecting the two devices and such that it can couple them when one has reached or is approaching one end of its stroke, and can be released when desired to permit the one device to move independently of the other. The releasable coupling preferably comprises a toggle linkage which is automatically brought into a position for locking when one of the reciprocable devices reaches or approaches one end of its stroke.

A control mechanism according to the invention, and the aircraft brakes controlled thereby, re preferably operated by gaseous pressure, which will normally be air-pressure and which is released from one or the other of the brake sets when the aircraft is to be turned. The mechanisms according to the invention can also be arranged, however, so that the brakes are operated by a liquid pressure or'a vacuum, and such constructional forms are intended to be included in. the scope of the present invention.

In order that the invention may be more clearly understood constructional examples thereof will be described in detail with reference to' the accompanying drawings in which- Figure 1 shows the arrangement of the connections between the main control and the auxiliary control devices of one form of a control mechanism according to the invention, with which form the brake mechanism is adapted to be operated by gaseous pressure; I

Figure 2 is a plan view of a main control device and auxiliary'control devices assembled into a unitary form, a 'remotecontrolmechanism for v the main contfoldevice then being provided;

Figure 3 is a sectional elevation on the line 3-3 of Figure 2, .and I j 4 is a sectional elevation on the line 4-4 of Figure 2;

Figure 5 is a central longitudinal section in a vertical plane of a modified form of auxiliary control device to that shown in Figure 4;

Figure 6 shows the arrangement of the connections between the main control device and auxthe air pressure to pass to the brakes. Locking means are represented at 3 which only permit the main control 'device' to be operated when .in the position shown in full lines, the position shown in dotted lines representing the'lo cking position.

The main control device as shown is constituted by a twist-grip control and when turnedia valve is opened which allows air-pressure to pass through the tube ID to the auxiliary control devices II and I2 by way of the branch tube connections I3 and I4. At the same time (i; e. on the initial operation of the main control) air is allowed to pass to both brake-sets on opposite sides of the centre line of the aircraft from the auxiliary control devices respectively associated with the two brake sets through the connections l5 and IS on the said latter devices and commuhL.

-24 efiects a longitudinal movement of the sleeve -25 slidably niounted in the cylinder 26 on an up;

eating with the actual brake mechanisms which are not shown in the drawings. The auxiliary control devices I l and l 2 are shown as adapted to be operated directly'by the rudder-bar l1, turning of which for steering purposes from the neutral position shown in the drawings brings it into contact with one or other of the members l8 or l9 associated with the auxiliary control devices II and I2 respectively and causing the operation thereof when moved by the rudder-bar.

Figures 2, 3 and 4 show a modified form of construction in which the main control device is assembled in close proximity to the auxiliary devices and is also provided with means whereby a remote control may be effected by the pilot of the operation of the said main control device. Further, the operation of-the auxiliary control device is effected indirectly from the rudder-bar" or equivalent mechanism by means of a suitable coupling provided therebetween. The connections for the passage of compressed air between the main control and the auxiliary control devices are similar to those shown in Figure 1, air from the reservoir (not shown in Figure 2) passing to the main control through the tube 20 (Figure 3) to a valve 2| which is preferably of the type known under the trade name of Schrader valve mounted in the member 14. This valve is controlled by means of the cable 22 (of the type known under the registered trade mark of Bowden cable) connected at one end to' the member 23, which is pivotally connected to the stirrup-shaped lever 24, and having the other end controlled by the pilot. Movement of the lever standing projection 2B6 formed on which cylinder the lever M is pivoted. Increased tension on the cable is arranged to move the sleeve to the right to the position shown in Figure 3 and 4 thereby compressing the spring 2'! which causes a return movement of the sleeve when the tension on the cable is released. Compression of the spring 21 causes movement of the piston 28'part of the stem of which is surrounded by the spring 45 21 located between the piston head and the sleeve 25 which surrounds the remainder of the stem in a manner permitting relative movement in the direction of the axis of the piston. The piston 28 is provided with a rubber face 29 which co-oper- 5 ates in the extreme right-hand position with a valve seating 30. The piston is provided with a cylindrical projection 3| at the rubber face which passes through a central axial orifice in the valve seating 30, and is provided further with 5 a projection 32 for co-operation with a valve pin 33 to efiect the opening of the valve 2| shown in an open position in Figure 3. The valve 2| when open allows air to pass from the supply-line 20 to the passage 34 and the pipes 35. As will be 60 seen from Figures 2 and 4 the pipes 35 each communicate with a passage 36 provided in an main control has been moved to put the brakes in operation, from the passage 33 in the member 14 to the passage 39 from whence it passes to a lower cylinder chamber 40 formed in the outer 75 casing ll attached to the member 14. This cylinder chamber is provided .with a piston 4| between the head of which and the head 42 of the cylinder 46 is provided a rubber'sleeve 43 which provides an air-tightcontainer of variable volume. The piston 4| is constructed to be of a suitable shape-to allow of'the rubber sleeve being accommodated between the piston and thecylinder walls when the piston is moved to the right in Figure 4. The free circular edges of the rubber sleeve are gripped at one end between the cylinder head 42 and the cylinder walls, and at the other end between the piston 4| and a cap or piston head member 10 which has a screw portion II to secure it to the piston. The piston 4| is moved out to the position shown in Figure 4 by the-passage of compressed air-to'the rubberwalled container.

Air may also pass when the main control is operated from the passage 36 through the holes 44 in -a valve sleeve, which holes .register with an annular passage 45 in the external member in which the valve sleeve is mounted. The passage 7 45 is arranged to be in communication with the passage 36. A further valve- 46 which is also preferably of the "Schrader" type is provided in the path of the compressed air issuing from the conduit 36 and is normally held in the open po-' sition by a piston not a construction similar to that of the piston 28 described in connection with the main controlshown in Figure 3. Thepisto'n 12 is held in a position to cause the opening of the valve 46 by the spring .41. After passing the valve 46 air passes to theactual brake mech anism not shown in the drawings by means of the connection 46.

The piston 12 which is under the action-ofthe spring 41 is mounted together with' the spring in a second hollow piston 46 which is normally held by a surrounding spring 466 inthe' position shown in Figure. 4 so as to maintain. the first piston I2 in the extreme right hand position to open the valve 46. The hollow piston 46 is slidably mounted in a cylinder chamber formed in the outer casing '13, and relative sliding movement between the two pistons 46 and I2 is also possible. The left hand end of the piston 46 is pivotally connected to a lever 56 .pivoted'at 5! between its end-points on a supportinggpivot formed or mounted on the external casing ",ahd connected at its other end 62 by means. of control elements 53, 54 to an extension is of the piston-4L The connections between the elements 64 and thepiston extension 66, the element 63 and'the lever 50, and between the elements themselves, are all of a pivotal nature. The elements .61 and 64 are constructed so as to, form a toggle. linkage.

It willbe seen that the movement or the piston 4| caused by'operation of the main control de' vice to apply the aircraftbrakes causes the linkage to be extended to the position shown in Figure '4. It will also be appreciated that the operation of the devices 31 and 68 being identical,

air will pass tothe brakes so as to apply equally the brakes or brake-sets on either side of the-centreline of the aircraft.

In the form of construction shown in Figures 2,

3 and 4 the auxiliary control devices are operated indirectly by the rudder-bar which is provided in operative connection with a devicem which may be moved about a pivot 566. Movement of the rudder-bar from one side or the other is arrangedto produce 'a. pivotal movement of the member 56 which results in'the co-operatlon of one of the members 51 or 66 provided thereon with associated with the auxiliary control devices 31 and 36. The members 66 and 66 arein rigid vconnection with the toggle-link 64 of their respective'auxiliary control devices and are so positioned that when subjected to pressure from the corresponding member 61 or 66 the toggle linkage is maintained in an extended or locked position and a return movement of the piston extension 56 cannot therefore cause the collapse of the toggle linkage but turns the lever 50 about the pivot Ii thereby effecting movement of the piston 46 against the action of the spring 409. Spring pressure on the valve operating piston 12 is thus reduced and the air-pressure causes it to move to a position in which the valve 46 may close under the air pressure and. the rubber face of the piston I2 itself move away from the annular seating. Closing of the valve 46 prevents ton extension through the passage 62 to exhaust.-

Release of one or other of the brake-sets on opposite sides of the-centre line of the aircraft is therefore effected by the turning movement of the rudder-bar.

The action of the piston 12 in allowing the brake pressure to be released will be better understood from the following further description ofthe main control device release of which, that is to say, release of tension on the cable 22, permits he sleeve 25 to move to .the left under the pressure of the spring 21 and air pressure on the piston 16 causes it to make a following movement. The piston movement allows the valve II to be closed byflie spring of the valve 46 and air pressure from the brakes not already re- 0 brakes are released by the main control and the auxiliary devices are then in a position readilyto be brought into operation by the initial application of the brakes by the. main control. It

will be noticed that this collapsed position leaves theriidder-bar, in the case of direct control of the auxiliary devices by the rudder-bar, as in the construction illustrated in Figure 1, free from any encumbrance of members causing the operation of the auxiliary devices.

It will be seen also that all the brakes in aircraft-brake control mechanisms according to the invention are equally applied in the first instance even although the rudder-bar may be moved out of its neutral position since movement of the 65 rudder-bar out of this position only occasions the release of the pressure of one or other of the brake-sets after the toggle linkage has moved out to its fullest extended and locked position. Since this latter movement is not possible when the rudder-bar is displaced from its neutral or approximately neutral position the auxi=iary control device in question cannot come into operation. Initial application of the brakes on land- .ing in an equal manner is thus ensured and greater safety is secured thereby since an initial (1. e. presumably while travelling at high speed) application of brakes in a difierential manner would probably result in the overturning of the aircraft.

Figure 5 shows a sectional view of an auxiliary control device which is a modification ofthat shown in Figure 4, and Figure 6 shows the connections provided between a reservoir for compressed air, a main control device and a pair of auxiliary control devices of a construction as shown in .Figure 5. f

The reservoir for compressed air is shown at I06 in Figure 6 and, branched pipe connections 80 pass respectively from the reservoir to a main control device represented at 8 and the auxiliary control devices represented at 83 and 84 respectively, that branch proceeding to the latter devices being itself branched at 8| and 82 so as to pass to both auxiliary devices. The main control device 8 has a pipe connection I83 passing therefrom to branch pipe connections |84 and I85 which also pass to the auxiliary control devices. The main control device, which may. be any suitable form of valve operable to allow or to restrain the passage of air from the reservoir, is shown in Figure 6 as a twist-grip control similar to that' shown in Figure 1. Q

Each auxiliary control device 88 (or 84) comprises an external casing similar to that denoted by the reference numeral 13 in Figure 4, and comprises also two reciprocable devices or pistons denoted by 4| and 49 similar to the pistons shown in Figure 4, and referred to in this latter figure by similar reference numerals.

The lower reciprocable device or piston 4| is similarly provided with a head member 18 for securing the end of a rubber sleeve 48, the other end of which sleeve is secured in the head of the cylinder'in which the piston 4| reciprocates. A

fluid channel 81 is provided in the member I4 which is secured to the external casing in a similar manner to the way in which the member 14 is secured to the outer casing 13 as shown in Figure 4. The passage 81 is in communication with the pipe I84 the passage of air through which is controlled by the main control device. A spring 88 is provided to act on the piston 4| and tends to maintain it in the position shown in Figure 5, displacement from which position is efiected against the action oi the spring by compressed air passing through the passage 81 from the pipe Figure requires the piston 49 to be in its extreme left-hand position and the compressive force exerted by the spring 41 upon the auxiliary piston 12 is ata minimum. The auxiliary piston 12 is similar to the piston member denoted by the same reference numeral in Figure 4 as regards its form and method of mounting and operation, and is similarly arranged to control the action of a valve- 46 (e. g. a Schrader valve) provided to control the passage of air to the conduit 48 leading to the braking mechanism. The fluid conduit leading to this valve, however, is now provided in direct connection with the reservoir the branch the conduit 81 and the lower piston member ll- .ismoved to the left the spring 41, consequent upon such movement, being compressed to an extent dependent upon the extent or operaton of the main control device, that is, upon the pres-" sure of the air admitted to the rubber sleeve 43. The compression of the spring 41 causes the piston 1.2 to open the valve 46 and compressed air passes from the reservoir to the brakes until a pressure in the'brake-set has been built up which is sufiicient to move the piston I2 to the leftby virtue of the pressure exerted on the face of the piston against the action of the spring 41. When this happens, air can escape from the brakes through the grooves 94 in the projecting portion of the piston and through the wire-drawing outlet 82. The valve 46 closes immediately the piston 12 makes any movement to the left, thereby cutting ofi communication between the pipe 48 and the reservoir.

It will be seen that in the arrangement described in connection withFigures 5 and 6 braking pressure is applied in accordance with the extent of operation of the main control device, the actual brake pressure existing in the brake-sets being respectively balanced against the compres- 3 sion produced in the spring 41 of the respective auxiliary control devices. It will be seen also that the member 60 is presented for co-operation with the rudder-bar or its equivalent mechanism upon operation of the main control device and in the present construction a differential braking eflect is immediately achieved if the rudder bar is not located in its central position and it is not necessary to zeroize the rudder-bar before a differential eifect can be obtained. The extent of the movement of the member 69 for cooperation with the rudder-bar is also in proportion to the extent of operation of the main control device. Each auxiliary control device is thus seen to comprise a valve controlling the braking pressure in its respective brake set, and loading means for the valve operated in accordance with the operation of the main control device. The loading means are also arranged to be modified according to the position of the rudder-bar.

The modified form of auxiliary control shown in Figure 5 may be provided in apparatus of the form shown in Figure 6 or may be provided in a unitary assembly such as shown in Figure 2 with the main control device, provided with attachments enabling the remote control of its operation to be effected, located between a pair of such auxiliary devices and a pipe 35 as shown in Figure 2 then being connected only with,the chambers 40, the pipe 36 not then provided and the valve 46 arranged to control communication between the reservoir and the brakes. A difference between a control mechanism employing the modified form of auxiliary controls shown in Figure 5 from one employing auxiliary controls of the form shown in Figure 4 is seen in the fact that the former arrangement has auxiliary controls to control the braking, the simultaneous action of which auxiliary controls is controlled by the main control device and the action of 7 which is also independently and separately modified by the respective auxiliary control devices. In both cases the main control device upon operation puts the auxiliary devices into a condition whereby movement of the rudder-bar causes one or the other of them to modify the reservoir are then dispensed with. The actual braking pressure in this form of construction results fromtwo reductions of the supply pressure. first at the main control device and secondly at the respective auxiliary control device. The regulation of the braking pressure is then found to be practically unafiected by the normal variations of the supply pressure. With such a construction the area of the lower piston is preferably such that a pressure of, say, approximately 40 lbs. loads the valve 47 to produce a braking pressure of approximately 30 lbs.

In all cases the constructions described in the foregoing specification have the auxiliary'con- 'trols or the unitary assembly of such controls preferably provided with a suitable form of con struction of their base portions to enable them to be conveniently mounted on a cross-member of the aircraft frame in proximity to the rudderbar or'associated or equivalent mechanism.

I claim: I

1. For the operation ofaircraft wheel brakes actuated by fluid pressure, a control mechanismcomprising in combination a main control device to control the simultaneous operation of two sets of brakes respectively operative on wheels situated on' opposite sides of the fore and aft centre line of the craft, a pair of auxiliary control devices and, to operate the latter, a rudder bar for the craft, each of which auxiliary control devices serves only one oi? the said brake sets and comprises a valve controlling the braking pressure in the respective brake set, loading means for the valve operated in accordance with the extent of operation of the main control device, means for releasing the braking pressure and an actuator for connecting the said releasing means with the rudder bar of the craft whereby movement of the rudder bar can produce a differential braking effect by release of braking pressure in the brakes on one side of the aforesaid plane substantially without alteration of the braking pressure in the brakes on the opposite side.

2. For the operation of aircraft wheel brakes,

a control mechanism according to claim 1 having an operative connection between the valve loading means and the actuator of each auxiliary control device so that the said loading means are operated in accordance with the movements of the actuator produced by movement of and by virtue of its cooperation with the rudderbar.

3. For the operation of aircraft wheel brakes actuated by fluid pressure, a control mechanism comprising in combination a main control device to control the simultaneous operation of two sets of brakes respectively operative on wheels situated on opposite sides of the fore and aft centre line of the craft, a pair of auxiliary control devices, and. to operate the latter, a rudder bar for the craft each of which auxiliary control devices serves only one of the said brake sets and comprises an actuator for the device, a valve controlling the braking pressure inthe respective brake set, loading means for the valve forming 5 part of an operative connection between the said valve and the actuator for the respective auxiliary control device and means to render the main control device operative on a part of said operative connection to control said loading means and at the same time cause the actuator to be moved into or out of positions for cooperation with the rudder bar, at which positions the actuator also controls said loading means in accordance with the position of the rudder bar.

4. For the operation of aircraft wheel brakes actuated by fluid pressure, a control mechanism according to claim 3 having the operative connection between the-actuator and the loading means for the valve controlling the braking pressure, comprising a toggle linkage which can only become locked for the transmission of movement of the actuator to the loading means when the rudder bar is moved to a position at which no differential adjustment is occasioned. 5. For the operation of aircraft wheel brakes actuated by fluid pressure, a control mechanism according to claim 3 having each auxiliary control device fitted with a compound valve comprising flrstly a release-valve normally open in a wire-drawing pressure outlet passage of the respective brake-set,- a slidable element and an actuator attached thereto, and a resilient connection between the release-valve and the slidable element the extent of the movement of which and the degree of correspondingcompression of the resilient connection depend on the operation of the main control device andalso on'the position of the rudder-bar which co-.operates with the actuator, and secondly a supply-valve nor- 40 mally shut in the pressure supply-passage of the brake-set but thrust open by the release-valve when the said release-valve is closed by the slidable element and reclosed when the air-pressure in the brake-set has overcome the release-valve and its aforesaid resilient connection.

6. Forthe operation of aircraft wheel brakes actuated by fluid pressure, a control mechanism according to claim 3 wherein the main control device comprises a hand operated valve located in a supply, conduit for fluid under pressure.

7. For the operation of aircraft wheel brakes actuated by fluid pressure, a control mechanism according to claim 3 wherein the main control device comprises a loaded valve controlling the braking pressure, a further valve located in the pressure fluid supp y conduit and arranged so as to be opened by the loaded valve only when the loading thereon exceeds the pressure of the fluid in the braking mechanism, and hand operated remote control means for loading means of the loaded valve.

8. For the operation of aircraft wheel brakes V actuated by fluid pressure, a control mechanism according to claim 3 wherein the main control device is provided with means for hand operated remote control and is assembled in a position between the auxiliary control devices so as to form a unitary therewith which may be mounted in the aircraft in a position close to the rudder bar and symmetrical with regard to the axis of rotation thereof.

' FREDERICK, JOHN 'ranrus. 

